Electrically-operated tool.



1. 5.1KNowLs0N. ELECTRIC-ALLY'OPERATED TOOL.

APPLICATION FILED JUNE 16,1915;

1,298,966., Y I Patented Apr; 1,1919.

4 SHEETS-SHEET 1.

I, S. KNOWLSON.

ELECTRICALLY OPERATED ooL.

APPLICATIQN FILED JVUNE 16| 1915.

Patented Apu 1,1919.

J4 TTU/UVE Y 4 SHEETS-SHEET 2 vEN TOR.

J. S. KNOWLSON.

ELEcmcALLv oPERATED Tool.

APPLICATION FILED )UNE 16. IBIS- Patented Apr. 1,1919.

J. S. KNOWLSON.

ELECTRICALLY OPERATED OOL.

APPLICATION. FILED luNE 1s. 1915.

4 SHEETS-SHEET 4.

STATES .PATENT OFFICE.

:finas s.v xNowLsoN, or oni: PARK, ILLINOIS, A'ssIGnoii. 'ro ELECTRO-MAGNETIC Toor..

conm, or

CHICAGO,` ILLINOIS, A CORPORATION OF ILLINOIS.

ELECTBICALL-OPERIATED TOOL.

Specication of lLetters Patent.

Patented Apr. 1, 1919.

i Application led June 16, 1915. Serial No. 34,523.

To all whom it may concern.'

KNowLsoNy current generator of low voltage, which is Be it known tliat I, JAMES'S.

a citizen of the United States', residing at Oak Park, in the county of .Cook and State' may vobviously erated percussion tool, for'riveting, drillingyf chipping, or other like purposes, of the general type shown in the ,patent to George H. Rowe, No. 938,7 09, patented November 2,

. 1909 and one of the Vprincipal objectsof the invention is to provide a tool of this character which may be operated from an alternat-V ing current circuit or, preferably, by either an alternating current or a direct current whichever is available. A tool of this type consists, generally speaking, of an electromagnet havingan armature, constituting the driven element of the tool, and means for shifting the field flux of the magnet by either moving the magnet itself or by imparting movement-for example, reciprocating movement,-to a sleeveof magnetizable metal, tlie ends of which sleeve are substan` .tially insulated from each other and which is interposed between the coil of the magnet and its armature core; 'By this means moyement is imparted to the driven or percussion element and the impacts thereof -against the tool shank are cushioned. If thepercussion element is reciprocated, as in a riveter, hammer or drill, the movements of reciprocation of the sleeve'are most conveniently effected by means of an electric motor contained in the casing ofthe tool. Inasmuch as direct current is very much to be preferred for energizing the' magnet, tools of this type have customarily been designed, so far as I am aware, for operation by direct current only. That is, they have been furnished with direct current motors for driving the sleeve; the motor and coil for magnetizing the sleeve being sometimes in series and sometimes in paralle Mv present invention contemplates furnishing the tool with an alternating current motor, yor preferably with a universally wound motor, so that the same tool may be used with either direct current or alternating current, whichever is available, and in order to supply the electro-magnet with di- `.construction. A further make an improvement in the reciprocating *,sleeve, whereby the expense of manufacturfication of the construction rect current, my invention, in the preferred embodiment, provides the tool with a direct driven by the motor. A generator so driven be employed, if desired, in connection with a tool of this type furnished with the ordinary direct currentgenerator.

Low voltage in the magnet circuit .has the "advantage 'of making the matter of insulation easier .andn furthermore, permits the use of heavier wire, thereby cheapeningy the object of the invention is to ing'the same. is vdecreased and a better bearing surface is provided for the driven element, the armature core.

A further object is tov provide certain l novel means, to be hereinafter described, for

preventing the armature from becoming displaced with respect to or breaking away from the sleevedue to inertia. I

The invention has for further objects such other new and improved constructions Yand devices relative to electrically operated percussion tools as will be hereinafter described and claimed.

The invention is illustrated, in a preferred embodiment, in the accompanying drawings, wherein- Figure 1 is a longitudinal sectional view of a drill constructed in accordance with my invention.

Fig. 2 is a view, in perspective, ciprocating sleeve. I

Fig. 3 is a sectional view taken online 3-3 of Fig. 1.

of the refor the Fig. 5 is a sectional view'on line 5-5 of Fig. 1;

Fig. 6 is a diagram illustrating the electrical connections.

Fig. 7 is a sectional view, diagrammatic in certain particulars, illustrating a modified form of the invention in which a synchronous motor is employed, and

Figs, 8, 9 ,and 10 are longitudinal sectional views illustrating a certain preferred modiof the plunger and sleeve for preventing the latter from breaking away from or getting out of step with the former; these three gures show' ing different relative positions of the parts of the same structure at dierent points in the .stroke of the machine.

Like characters of reference designate like parts in the several figures of the drawings.

The operating parts of the device are inclosed in a casing consisting of a casting 10, a cylindrical member 11, a cap 12, closing the end of the cylindrical member, and a head 13 which is threaded into a cylindrical extension 14 on casting 10. The members 11 and 12 are secured to the main casting 10 by tie rods 15 threaded into lugs 16 on member 10 and engaged at their outer ends by nuts 17. Head 13 is formed with a boss 18 in which is a bushing 19 to receive the end of the tool shank 20. Attached to the casing is a handle piece and gear case 21 formed with a hand grip 22 which is hollow so as to make a place for the push button switch 23 by means of which the supply current to the operative mechanisms of the tool is controlled.

24 is an electro-magnet, the spool of which 25 is held between a boss l26 formed on the casing member 10 and la boss 27 on'the head 13. In the magnet is a non-magnetic bearing 28 within which slides a sleeve 29 (Fig. 2), made of iron or steel with the middle portion 30 cut away so that it is relatively thin. The sleeve, therefore, consists of two pole pieces connected by a cylindrical body which contains such a small amount of metal that to all intents and purposes the pole pieces are magnetically insulated one from another.

Within the sleeve is a solid core 31 made of iron or steel and formed with a hardened projection 32 adapted to strike the inner en-d of the tool shank 20.

The sleeve 29 is reciprocated by an electric motor, preferably a universally wound motor, capable of operation either by alternating or direct current. 33 indicates the field of the motor and 34 the armature, the latter 'being carried on a shaft 35 mounted in ball bearings 36 in the ca 12 and at the other end in ball bearings 3 arranged in a boss 38 formed in a web 39 on the central casing memberlO. On one end of shaft is a gear wheel 40 meshing with a gear wheel 41 on acountershaft 42 which turns in ball bearings 43 located in a boss 44 formed on the web 39. The sleeve 29 is connected by a connecting rod 45 with a wrist pin 46 on the gear wheel 41, the connecting rod being attached to lugs 47 on the upper end of the sleeve by means of a connecting pin l,48. Preferably a ball bearing 49 is interposed between the connecting rod and wrist pin.

The armature 50 of the generator is preferably carried on the armature shaft 35 of the motor. 51 indicates the field coils of the generator and 52 the pole pieces, the generator being of the low voltage type. 53 designates the brushes for the motor commutator 54, and 55 the bruslwfor the generator commutator 56. The motor is shown as series wound, 57 (Fig. 6) indicating the circuit and 58 the source of current supply. The field 51 of the generator is in shunt with the commutator of the generator; 59 (Fig. 6) indicating this circuit. The magnet 24 is supplied with 'direct current from the generator through a circuit 60; the armature windings on shaft 35 are insulated by means of a disk 61.

In the construction sho-wn in Figs. 1 and 2, the end of the sleeve 29 is closed and the sleeve formed with exterior longitudinal slots 63 communicating lwith the interior of the sleeve through perforations 64. At the end of the out-stroke of sleeve 29 and core 31, the core is forced inwardly of the sleeve thereby closing air ports 64. This produces an air cushion between the core and the inner end of the sleeve. The outer end of the sleeve is closed by an annulus 65, the opening in which is a trifle larger than the diameter of the projection 32 on the core 3l. 0n the back stroke' the lag of the core tends to throw it out of its proper position in the sleeve. This is prevented by the cushion of air between the core and the annulus 65.

The operation of the device is as follows: The operator grasps the machine by hand grip 22. By pressing the push button of switch 23 the motor 33, 34 is set in operation revolving gear wheel 41, which causes recip-v rocation of sleeve 29. At they same time a.

low voltage direct current is generated by generator 50, 51 by means of which magnet 24 is energized. I have found that there is always residual magnetism in the pole pieces of the generator field to start up the generator.v If such were not the case it would, of course, be possible to employ permanent magnets in the field of the. generator. The reciprocation of sleeve 29 shifts or distorts the magnetic field produced by magnet 24. This imparts reciprocating movement to the core 31. The relation between the core and the sleeve is, of course, an elastic one due to the magnetic attraction existing between these elements. This magnetic spring is supplemented by the air cushioning arrangements between the core and the inner and outer ends of the sleeve. The primary ob-v 'ject of having an air cushion at each end of the core is to-maintain-fthe core in a central position in the sleeve so that the impacts of the core against the tool shank 20 will be uniform. In other words, the air cushion stiffens the magnetic spring. In small machines it would be feasible to omit the magnet 24 and rely entirely on the air cushions to center the plunger on the reciprocating sleeve. I prefer, however, to employ the magnet primarily for this purpose.v

The expedient of turning down the center portion of the sleeve 29 so as to provide pole pieces substantially insulated magnetically from each ot-her instead of forming the sleeve with openings, as in the patent above referred to, has the advantage of economy of manufacture and also provides a perfectly smooth bearing of maximum area on the interior of the sleeve for the core 31.

In Fig. 7 I have illustrated a modified form of the invention according to which the machine is driven by a synchronous motor. The motor is in the nature of a synchronous converter having a commutator for the purpose of delivering direct current for excitingy the field of the solenoid 24.

The motor has a revolving armature, the windings thereof being connected in the usual manner, at one end to the collector wings 68, 69, and at the other end to the commutator segments 67. The pole pieces 71 are provided with short circuited bars 72. The connections between the shaft of the rotor and the reciprocating' sleeve 29 are the same as in the machine previously described. The motor is started by current' introduced into the windings of the armature through the commutator 67.

74: indicates the supply circuit in which is arranged a bi-polar double-throw switch 75. In one position of the switch (the one shown in Fig. 7) the supply leads 7 4: are connected with conductors 76, 77, which run to the brushes 78 of the commutator. 1/Vhen the motor is revolving in frequency with the supply circuit the switch 75 is reversed, cutting out the circuit 76, 77 and connecting with the supply leads conductors 79, 80 which lead to brushes 81, 82 bearing, respectively, on the slip rings 68,69. The magnet 24a is connected by wires 83, 84 with the commutator brushes. The current taken through this circuit is, therefore, transformed from alternating to direct current. The field coil 73 on the motor is also shunted by means of wires 85, 86 from the commutator brushes. The short circuited bars aid the motor in starting. It is not so essential, when these bars are used, to bring the motor to synchronous speed before throwing the switch 75.

In Figs. 8 to 10 inclusive I have shown`a modification in the construction of the magnetizable sleeve for reciprocating the percussion element or core, the purpose of which modification is to more e ectuallyl prevent the core from getting out of stepor breaking away from the sleeve when the latter is run at a very high speed, for example. This arrangement may be used either in place of the air cushion arrangement shown in Fig. 1

or as supplementing the same. It consists essentially of placing at oppos'te ends of the core or percussion element 31" magnetizable elements or disks 87, 88 which are movable The magnetic attraction with the core within the reciprocating sleeve 29b but are arrested in their movement as -the core reaches the end of itsstroke m each direction so that magnetic stresses are produced between such elements and the ends of the core which counteract thel inertia of the core. en d of the sleeve to which the connecting rod is attached, is shown as formed with a central perforation through which passes a bolt 89 threaded into the end of the sleeve. The bolt has a head 90 against which the disk 87 is brought by a movement of the disk and core toward the outer end of the sleeve. The disk 88 is shown as formed with lugs 91 which project into guide slots 92v formed in the outer ends of the sleeve. The latter is preferably closed by a head 93 which fits the striking element 32a on the core rather loosely. The movement of disk 88 inwardly The disk 87 within the of the sleeve is limited to the length of the lguide slots.

In Fig. 8 the parts are shown in the position which they will assume at the middle of the stroke, the in-stroke for example. between the disks and thecore holdthe disks and the core. together. When the sleeve reaches the end'of the iii-stroke (or possibly just before this) the force of inertia tends to throw the core inwardlyY of the sleeve. If this movement is excessive so that by the time the out-stroke of the sleeve occurs, the core has not reassumed its normal position, the effective operation of the machine is impaired.

But, as shown in Fig. 9, after the core has moved inwardly a certain distance, the inward movement of the disk 88 is arrested and any further relative movement of the core with respect to the sleeve is checked by the magnetic stress between thedisk and the end of the core. This stress very considerwhich they will assume (so far as I can determine it from theoretical considerations, observation being obviously impossible) at the end of the out-stroke or the beginning of the. in-stroke.l At this point the disk 87 comes against the head 90 of bolt 89 and any further movement of the core outwardly, or

assuming that the momentum of the core has been arrested byv impact against the tool shank, any tendency of the sleeve to pull away from the core is checked by the maggetting lout of place in the sleeve is checked.

Before this can' happen the thrust on the core must overcome the magnetic attraction between the core and one disk or the other, the force of which is considerabie.

While I have described my invention in certain preferred embodiments, it will be understood that modications might be lmade without departure from the spirit of the invention. Therefore I do not wish to be understood as limiting the invention except so far as the claims are specically so limited,

I claim:

l. In apparatus of the character de scribed, the combination of an electro-magnet and armature therefor; means for producing a shifting of the magnetic iield dun which carries the armature with it; and a generator driven by said means for energizing said magnet.

2. In apparatus of the character described, the combination of an electro-magnet and armature therefor; means comprising an electric motor for producing a shifting of the magnetic field Eux which carries the armature with it; and a generator driven by said motor for energizing said magnet.

y 3. In apparatus of the character described, the combination of an electro-magnet and armature therefor; means comprising an electric motor for producing a reciprocatory shifting of the magnetic field flux which ca-rries the armature with it; and a generator driven by said motor for ener.- gizing said magnet.

4.-. In apparatus of the character described the combination of an electro-magnet and armature therefor; means comprising an electric motor capable ofoperation by alternating currents for producing a reciprocatory shifting of the field fiux of said electro-magnet which carries said armature with it; and a generator, the armature of which is 'on the same shaft with the armature of the motor, for supplying direct current to said magnet.

f 5. In apparatus of the character described, the combination of an electro-magnet; a

rfloating core armature in said magnet,"a

magnetizable sleeve interposed between the magnet and core; a motor to reciprocate said sleeve, and a generator driven by the motor for supplying current to said electro-magnet. v

6. In apparatus of the character described, the combination of an electro-magnet; a

said

Lacasse floating core amature in said magnet; a

Vsleevetot magnetizable metal arranged withmagnet and formed so as to provide a pair of spaced pole'pieces; a iioating core in said sleeve' a series wound universal motor a gear wheel on the armatures'hat oi motor; a gear wheel lmashed with the rst named gear wheel provided with a wrist pin; a connectin rod which connects the sleeve with said wrist pin; and a generator, the armature of which is carried on the armature shaft of the motor having a rommutator, the brushes of which are in 'circuit with said electro-magnet, the held of the generator being in shunt with said co v tator.

8. In apparatus ofthe character described, the combination with an electro-magnet and armature; of an alternating current motor p the electro-magnet which carries the armature with it; and means operated by the m0- tor for supplying direct current to said electro-magnet. y

9. In apparatus of the character described the combination `with an electromagnet and armature; of an alternating current motor for producing a reciprocatory shifting of the field flux of the electro-ma et which carries the armature with it; an means operated by the motor for supplying direct current to said electro-maglie 10. Inv apparatus of the character described, the combination of 'an electro-mag net, a floating core armature in said magnet, a magnetizable sleeve interposed between the magnet and the core; and a motor adapted to e operated by alternating currents to `reciprocatel the sleeve provided with means for supplying a direct current to the coil of said electro-magnet 11. In apparatus of 'the character described, the combination of an electro-magnet, an armature corev therefor, a"magnet' the tendency of the core to get out of step with the sleeve.

12 In apparatus of the character described, the combination with an electromagnet having` a oating core armature, means for producing shifting movements 1n opposite directions of the eld of the magnet so as to reciprocate the core, magnetizable elements movable WithV the core and Within the field of said magnet, and means for arresting the movements of said elements as the core reaches the ends of its stroke opposite directions for the purpose scribed.

JAMES S. KNOWLSON. Witnesses:

L. A. FALKENBERG, R. KUEHN. 

